Fix order and grouping of cask stanzas

[waldyrious]

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I found some inconsistencies when I started preparing the documentation update after #8137. This PR makes the following changes:

• Put desc stanza after the name stanza (I mistakenly introduced it to the wrong array position in Add a desc stanza to the cask DSL #8137)
• Add missing language stanza to its own group, as shown here.
  • I also adjusted the test that used this stanza, to conform to the stanzas within the same group should have no lines between them rule.
• Add missing vst3_plugin stanza to the group containing vst_plugin, as shown here

Should there also be a target stanza here, according to this?

[waldyrious]

I see from the failing tests that the existing casks that use the language stanza fail the same brew style issue that I had to address in test/support/fixtures/cask/Casks/with-languages.rb. I can think of some ways to address this:

• Edit the casks in Homebrew/homebrew-cask to remove the blank line between language blocks
• Make an exception for the language stanza in the stanzas within the same group should have no lines between them rule.
• Keep the language stanza out of the sorting/grouping validation (as it was before)
• Something else

How should I proceed?

[reitermarkus]

Please open a separate PR for the language stanza order so we can merge the fix for desc.

Should there also be a target stanza here

No, that's an attribute for the artifact stanza.

[reitermarkus]

Thanks, @waldyrious!